Method of brittlizing pencil sheaths



l atentecl June 13,

UNITED PATENT oFi leE 2510,2341 Mii'r'iioii or iiiti if'iiilizind amen Jeni ii. Ate, and iii; Mine-anew Brunswick; N. J.; assignors to Joseph Dixon Grucible' Gompairy; Jersey City; N: J:; a; corporation of New Jersey No Drawing'; Aiiiilicatidii Afiir'i'l t2; i920; Serial No. 85?;166

6 Claims. (01. 1-41?) l This invention relates to pencils and particu'- larly to paper wrapped pencils or pencils in which the core of marking material is enclosed in a convolute sheath of paper, preferably newsprint paper, the successive convolutions being sec-mes together by a suitable adhesive. O'iie typep'f ma-' chine for formingsuch a pencil is shown in Mil ler Patent No. 2,259,959 of October 21, 1941.

However, in order to produce a paper pencil which could be sharpened with a knife or in a mechanical pencil sharpener, it was found necessary to brittlize, char or age the paper, and Miller Patent No. 2,352,444, issued June 27, 1944, discloses a machine developed for brittlizing the paper prior to winding the paper into a sheath around the pencil core. Although this sequence of operations produces a satisfactory pencil, the brittlized paper is more difficult to handle in the sheath forming machine and this invention has been developed in order to overcome this difficulty.

This invention has for its salient object to provide a method of so brittlizing paper pencil sheaths that the major portions of the moisture therein will be removed and the brittlized sheath will thereafter remain moisture resistant.

Further objects of the invention will be evident from the following specification.

The paper used for making pencil sheaths of the type above described is preferably newsprint paper, which is composed of cellulose and lignin, but sulphite pulp in amounts up to 40% may be added to make it more stable.

The paper sheet or web is wound into a convolute sheath with a suitable adhesive, such as sodium silicate, between successive convolutions. A core of suitable marking material, such as the conventional clay-graphite leads, is disposed in the center of the sheath.

The sheath so formed and comprising the core, paper sheath and adhesive contains, by weight, about 24% of water, about half of which is in the paper and half in the adhesive. The problem is to get rid of the major portion of this water in such a manner that the pencil will not thereafter absorb sufi'icient moisture to prevent sharpening the pencil.

It has been found that this cannot be accomplished by the obvious method of subjecting the pencil to a brittlizing temperature of 390 to 400 F. Pencils so treated again absorb moisture very quickly and in such quantity as to render them unfit for use.

However, by experiments it has been determined that if the article is slowly predried until then it can be subjected to the bilittlizing te per:

ature of ap roximatel sec-400 F: and wi l? thereafter be stable and: resistant to softening by moisture even when subjected to long exposure to .hum-id weather conditions;

by exposing the pencils to open, relatively dry air for twenty-four hours or longer, or by subjecting them to heat at not more than 250 F. a relatively short time, such as approximately ninety minutes, or by subjecting them to a temperature gradually raised from room temperature to not over 250 F. for approximately two hours. If desired, any of the foregoing preheating operations can be accelerated by the use of a warm air blast.

After the pencils have been preheated by any of the above methods, they are thereafter subjected to a brittlizing temperature of approximately 390400 F. for thirty to forty-five minutes. When so treated the pencils will remain substantially stable as to moisture content and will not thereafter absorb moisture to an extent rendering them unfit for use or difiicult to sharpen by knife or a mechanical sharpener. v

The foregoing method of treatment may be used for pencils having a core of such composition that it will not be damaged by the brittlizing heat. For instance, it can be used effectively with the conventional clay-graphite composition. This material has voids filled with a waxy substance to give it water-proof and smooth writing properties. When pencils having leads so constituted are treated as above described, only a small fraction of the lead is forced out by expansion at the temperature of 400 F. and the remainder is sufiicient for the intended purpose.

Although one specific embodiment of the invention has been particularly described it should be understood that applicants do not intend to limit the scope of their invention to the specific and exact details except as to the limitations imposed by the following claims.

What we claim is:

1. The method of brittlizing sheaths of pencils having a convolute sheath of paper, adjacent convolutions being secured by adhesive, said method consisting of predrying the pencils in a temperature not exceeding 250 F. and thereafter subjecting the pencils to a brittlizing temperature ranging between approximate temperatures of 390-400 F.

2. The method of brittlizing sheaths of pencils having a convolute sheath of paper, adjacent convolutions being secured by adhesive, said method 3 consisting of predrying the pencils in a temperature not exceeding 250 F. until approximately 70% of the water has been eliminated, and thereafter subjecting the pencils to a brittlizing temperature ranging between approximate temperatures of 390-400 F.

3. The method of brittlizing sheaths of pencils having a convolute sheath of paper, adjacent convolutions being secured by adhesive, said method consisting of predrying the pencils in a temperature gradually raised from room temperature to a temperature not exceeding 250 F., and thereafter subjecting the pencils to a. brittlizing temperature ranging between approximate temperatures of 390-400 F.

4. The method of brittlizing sheaths of pencils having a convolute sheath of paper, adjacent convolutions being secured by adhesive, said method consisting of predrying the pencils in a temperature gradually raised from room temperature to a temperature not exceeding 250 F. until approximately 70% of the water has been eliminated, and thereafter subjecting the pencils toa brittlizing temperature ranging between approximate temperatures of 390-400 F.

5. The method of brittlizing sheaths of pencils having a convolute sheath of paper, adjacent ing between approximate temperatures of 390-4il0 F.

JOHN E. AKE. KAY MILLER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,222,152 Smith Apr. 10, 1917 2,375,616 Miller May 8, 1945 

1. THE METHOD OF BRITTLIZING SHEATHS OF PENCILS HAVING A CONVOLUTE SHEATH OF PAPER, ADJACENT CONVOLUTIONS BEING SECURED BY ADHESIVE, SAID METHOD CONSISTING OF PREDRYING THE PENCILS IN A TEMPERATURE NOT EXCEEDING 250*F. AND THEREAFTER SUBJECTING THE PENCILS TO A BRITTILIZING TEMPERATURE RANGING BETWEEN APPROXIMATE TEMPERATURES OF 390*-400*F. 